Driving arrangement for passive time indicating devices

ABSTRACT

A driving arrangement for passive time indication devices wherein a passive indication device is connected between the output terminal of a double throw-type switching element and a terminal having a first potential such that the difference between said first potential and a second potential applied to the output terminal of said switching element when said switching element is in a first position is sufficient to excite the passive time indication device while the difference between said first potential and a third potential applied to said switching element output terminal when said switching element is in a second position is less than the threshold voltage of the passive time indication element.

United St:

Hama et al. May 6, 1975 [54] DRIVING ARRANGEMENT FOR PASSIVE 3,575,4924/1972 Nester et a1. 350/160 LC TIME INDICATING DEVICES 3,576,099 4/19713,664,118 5/1972 Inventors: Teisum Hama; zuh shi a, 3,700,306 10/1972Cartmell et al 350/150 both of Suwa, Japan [73] Assignee: KabushikiKaisha Suwa Seikosha, Primary Examiner--Edith Simmons J ackmon Tokyo,Japan Attorney, Agent, or FirmBlum, Moscovitz, Friedman 22 Filed: Mar,19, 1974 Kapla 21 Appl. No.: 452,588

ABSTRACT Related US. Application Data A [63] Continuatiomimpan of No232,461 28, A driving arrangement for passive time indication de- 1972'Pat 3,797,225 vices wherein a passive indication device is connectedbetween the output terminal of a double throw-type [30] ForeignApplication Priority Data switching element and a terminal having afirst poten- Feb 27 971 Japan p 463804 tial such that the differencebetween said first potential and a second potential applied to theoutput termi- [52] Us. Cl" M 58/50 307/38. 340/336. nal of saidswitching element when said switching ele- 350/160 ment is in a firstposition is sufficient to excite the pas- 5 Int Cl. G04) 19/30. HOZj3/10. o 39/02 sive time indication device while the difference be- [58]Field 58/50 340/324 tween said first potential and a third potentialapplied 6 350/160 to said switching element output terminal when saidswitching element is in a second position is less than [56] ReferencesCited the threshold voltage of the passive time indication el- UNITEDSTATES PATENTS emem 3,505,804 4/ 1970 Hotstein 58/50 R 9 Claims, 16Drawing Figures LEfiK/FGE 9 45444765 Ies srae /4 wa/mme 2 EME/V? /0 ORIN "es/50R DRIVING ARRANGEMENT FOR PASSIVE TIME INDICATING DEVICES CROSSREFERENCE TO RELATED APPLICATION This is a continuation-in-part of ourco-pending application Ser. No. 232,461, filed Feb. 28, 1972 which isnow US. Pat. No. 3,797,225.

BACKGROUND OF THE INVENTION This invention relates to a drivingarrangement for passive time indication devices adapted for actuation byan electric signal to provide a visual time indication in electrictimepieces. In recent years. passive time indication elements such as.liquid crystal display devices have been produced which change thecondition of scattering, absorption, transmission or polarization oflight in response to an electric signal in order to provide a visualdisplay. Such passive time indication devices generally require smallamounts of power for operation and are particularly suitable forapplication to fully electronic watches, and in particular,- tosmall-sized fully electronic wrist watches. On the other hand, suchpassive indication devices generally require a high voltage foroperation, resulting in the problem that a slight leakage current in thedriving circuit reduces the efficiency of the indicating function. Bytaking into consideration the voltage characteristics of such passivetime indication elements, the foregoing deficiencies have beeneliminated.

SUMMARY OF THE INVENTION Generally speaking, in accordance with theinvention, a driving arrangement for passive time indication devices isprovided wherein a passive time indication deviceis connected betweenthe output terminal of a double throw-type switching element and aterminal having a first potential applied thereto. Said switchingelement may consist of a pair of separate switches connected to a commonoutput terminal, mechanical switching devices, and solid state switchingdevices. Second and third potentials are respectively applied to the twoinputs of said switching element for respective application to saidoutput terminal when said switching element is one of first and secondswitching modes. The value of said first potential is such that thedifference between said first and second potentials is sufficient forexciting said passive time indication element while the differencebetween said first and third potentials is less than the thresholdvoltage of said passive indication element.

Accordingly, it is an object of this invention to provide a drivingarrangement suitable for driving passive time indication elements toprovide time indication for watches.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification anddrawings.

The invention accordingly comprises the features of construction,combination of elements, and arrange ment of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a graphical representation of the typical voltage-brightnesscharacteristics of a passive indication element;

FIG. 2 is a block diagram of a general driving circuit for such passiveindication element;

FIG. 3 is a block diagram illustrating the driving arrangement inaccordance with the invention for such passive indication elements;

FIG. 4 is a circuit diagram of a second embodiment of the doublethrow-type switching element in accordance with the invention FIG. 5 isa circuit diagram of one embodiment of the driving arrangement inaccordance with the invention;

FIG. 6 is a block diagram of an electronic watch incorporating thedriving mechanism in accordance with the invention;

FIG. 7 is a circuit diagram of a circuit for producing the threepotentials required in connection with the driving arrangement inaccordance with the invention;

FIGS. 8, 9 and 10 are plots of strength of transmitted light v. peakvoltage of applied voltage for duty ratios of I, A and A respectively;

FIGS. 11a depicts a one digit of a seven bar display, FIG. 11b depicts afour-digit digital display formed of seven-bar displays, FIG. 11cdepicts selected waveform diagrams for driving the display of FIG. 11c.-

FIG. 12 depicts a driving circuit for' driving the display of FIG. 11b:and

FIGS. 13 and 14 respectively depict a modification of a portion of thedriving circuit of FIG. 12 for the cases where the display includes sixand eight digits.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, agraphical representation of the voltage-brightness characteristicsgenerally found in passive time indication elements is depicted. In saidgraphical representation, the axis of abscissa x represents the voltageapplied to the passive time indication element with the origin beingtaken at 0 The axis of ordinates y represents the brightness of saidpassive time indication element relative to a maximum effective valuefor indication assigned the value of 1. Curve 1 is a voltage-brightnesscurve in which the brightness is low between the originO and a voltage Vwhile between said voltage V and a voltage V, there occurs a change fromthe low brightness state (not excited state) to the high brightnessstate (excited state).

In addition, curve 1' shows the relation between voltage and thebrightness in the reverse situation to that of curve I. The voltage V isreferred to as the threshold voltage in this application.

As shown in FIG. 2, when a series circuit consisting of a passiveindication element 4 and a switching element 5 is inserted betweenvoltage sources 2 and 3, and when a leakage resistance 6 present duringthe opened state of switching element 5 is small, the divided voltageapplied to the passive indication element 4 may exceed the thresholdvoltage V so that said passive indication element approaches the excitedstate. The addition of a shunt resistance parallel to the passiveindication element to compensate for the above-mentioned undesirableresult is likewise undesirable, since the value of the resistance neededmust be smaller than the leakage resistance 6, thereby increasing theportion of the current which is unavailable for display purposes.

The arrangement in accordance with the invention as illustrated in FIG.3. wherein a first voltage source Va is connected between terminals 7and 8 and a second voltage source Vb is connected between terminals 7and 9, said second voltage source being of a value not less than saidfirst voltage source. The input terminal of a double throvwtypeswitching element 11 is also connected between terminals 7 and 8, saidswitching element having a common output terminal 12 for selectiveconnection to either of terminals 7 and 8. A passive indication elementis connected between terminals 9 and 12 while leakage resistors 13 and14 are connected between the respective input terminals 7 and 8 ofdouble throw-type switching element 11 and passive indication element 10(terminal 12).

As more particularly shown in FIG. 4, while a unitary double-throwswitching element as depicted in FIG. 3, may be used. said double-throwtype switching element may also take the form of two single-throwswitching elements 15 and 16 which operate oppositely, or by any elementhaving a similar function.

In the switching mode where terminal 12 is connected to terminal 7through the double-throw type switching element. passive indicationelement 10 is connected between terminals 7 and 9, so that the voltageof the second voltage source Vb is applied thereto. On the other hand,in the switching mode wherein terminal I2 is connected to terminal 8through said double-throw-type switching element. passive indicationelement 10 is connected between terminals 8 and 9. so that thedifference in voltage between said first and second voltage sources Vaand Vb are applied thereto. By insuring that the second voltage sourceVb is of a value great enough to excite passive indication element 10,and by insuring that the voltage of the first voltage source Va is of avalue less than the value of said voltage of said second voltage sourceVb by an amount within the range wherein said passive indication elementwill not be excited (i.e.. a value less than the threshold voltage). theexcitation condition of the passive indication element can be regulatedby setting the switching mode of double throw'type switching element 11between two values.

By selecting the first voltage source so that it has a value less thanthe second voltage source. it is possible to use semiconductor switchingelements having nonlinear leakage resistance in response to voltage asthe double throw-type switching element. An example of such anarrangement is depicted in FIG. 5, wherein the double throw-typeswitching element consists of an enhancement type P-channel insulatedgate field effect transistor 23 and an enhancement type N-channelinsulated gate field effect transistor 24. The passive indicationelement 22 is in the form of a nematic liquid crystal. Taking thepotential at a terminal 17 connected to the source of transistor 24, afirst positive potential is applied to terminal 18 connected to thesource of transistor 23 and a second positive potential sufficient toexcite indication element 22 and a value not less than the value of saidfirst positive potential is connected to terminal 19, which in turn isconnected to one side of passive indicator element 22, the other side ofsaid pas sive indicator element being connected to common outputterminal 21 connected between the respective drains of transistors 23and 24. The difference between the second positive potential and thefirst positive potential is selected to be smaller than the thresholdvoltage of passive indication element 22.

The control of the double throw-type switching element of FIG. 5 isachieved through terminal 20 connected to the respective gates oftransistors 23 and 24. Thus, said transistors are placed in a firstswitching mode when a potential nearly equal to the potential ofterminal 17 (approximately zero potential) is applied to terminal 20. Inthis mode, gate G of transistor 24 is placed at nearly zero potential sothat the resistance between the source S and the drain D thereof isplaced at an extremely large value. On the other hand. the gate G, oftransistor 23 is given a potential of one direction so that theresistance between source 5,, and drain D decreases substantially. As aconsequence, the potential at the common connecting electrode 21 betweenthe respective drains of transistors 23 and 24 becomes equal to thefirst positive potential applied to terminal 18 and a voltage nearlyequal to the difference between the second and first positive potentialis applied to passive indication element 22. Since this differencepotential is lower than the threshold voltage of said passive indicationelement, said element is not excited. At this time, if the currentflowing from terminal 19 to terminal 21 exceeds the current flowing fromdrain Dy of transistor 24 to terminal 17, drain D of transistor 23assumes a positive potential relative to terminal 18. However, since adiode has been formed in one direction between drain D,- of transistor23 and the substrate SH]: thereof. the potential in question becomesalmost equal to the potential of terminal 18.

In the second switching mode, wherein a positive potential nearly equalto the potential of terminal 18 is applied to terminal 20, gate G oftransistor 23 is placed at nearly zero potential so that the resistancebetween source S,- and drain D thereof are brought to an extremely largevalue. On the other hand, the gate G of transistor 24 has a potential ofone direction applied thereto so that the resistance between source Sand drain D thereof is reduced considerably. For this reason, thepotential at common connecting terminal 21 is substantially at thestandard potential (zero potential) and a potential nearly equal to thesecond positive potential is applied to passive indication element 22 toexcite said element.

While in the foregoing embodiment, a pair of transistors wasincorporated as the double throw-type switching element, other suitabledouble throw-type switching elements may be substituted thereforconsisting either of unitary switching elements or combinations ofswitching elements. provided the functions of the double throw-typeswitching elements of FIGS. 3 and 4 are performed.

Referring now to FIG. 6, a block diagram of a watch incorporating thedriving arrangement in accordance with the invention is depicted. Insaid embodiment, the double throw-type switching element may take theform of a complementary insulated gate field effect transistorarrangement such as is depicted in FIG. 5. Further. the passiveindication elements are of the nematic liquid crystal type, theindication elements providing a digital display of hours and minutesthrough the use of a seven bar display capable of displaying any numberfrom O to 9 at each digit of said hour and minute indication. For thispurpose. each digit would be represented by a liquid crystal displaydevice of the passive indication type having a common electrode, a

segmented electrode formed from said seven bars and liquid crystalmaterial of the nematic type therebetween. lndication of seconds isformed by means of a round liquid crystal display having six pie-shapedsectors which are sequentially flickered in response to a signal havinga period of one second, each of the pieshaped sectors being flickeredfor a period of seconds.

In the electronic watch of FIG. 6, a high frequency time standard signalis generated in an oscillator and divided into a signal having al-second period by a frequency divider 26. The l-second signal fromdivider 26 is applied to a [/10 divider 27 which serves to count thel-second signals to produce a lO-second signal for application to l/6divider 28. Divider 28 counts the 10- second signals to produce al-minute signal for application to the next stage.

The state output of 1/6 counter 28 is applied to a decoder 32 adapted toproduce six output signals, one of said output signals being associatedwith each of the sectors of the second indicator. Said output signalsare applied to gate circuits 36 which consist of six AND gates 54, oneof which is associated with each second indicator sector, for receivingthe associated output signal from decoder 32 and a l-second signal fromterminal 56 connected to the output of divider 26. The output of eachAND gate 54 is connected to the control of a double throw-type switchingelement 55, in this case to the respective gates of the insulated gatetype field effect transistors, to control the switching mode of saidswitching element. The input terminals of each switching element 55 indriving circuit 37 are respectively connected to ground potential V,;and to potential V The output terminal of each of said switchingelements is connected to one of the sector electrodes 45 of the secondindicator, the common electrode 47 thereof being connected to voltage VIn this manner, each sector is sequentially flickered at a frequency ofone Hz for a period of 10 seconds.

A l/lO divider 29 receives the l-minute signal from divider 28 throughOR gate 48, and produces a l0- second signal output. The state output ofdivider 29 is applied to a decoder 33 for producing seven outputscorresponding to the seven bars on the minute digit display segmentedelectrode 44. Each output of decoder 33 is applied to a doublethrow-type switching element 55 in driving circuit 38 which functions ina manner similar to the double throw-typer switching element 55 ofdriving circuit 37. In a similar manner, divider receives the 10-minutesignal from divider 29 through OR gate 48 to produce a l-hour signal.The state signals of divider 30 are applied to decoder 34 to drivingcircuit 39 which provides the driving voltages for the seven bar displayof the IO-second digit represented by segmented electrode 43.

Finally, the 1-hour signal output of 1/6 divider 30 is applied to a l/l2divider 31, the state of which drives the 10-hour digit segmentedelectrode 42 through decoder and driving circuit in the same manner asthe other digits of the display. A switch 52 resets the states of therespective frequency dividers and counters to their initial statesthrough a connection to terminals 53 thereof, while switches 49, and 51set the respective digits of the l-minute display the lO-minute displayand the l-hour display to the desired figures by connection to therespective OR gates 48. Each time one of switches 49, 50 and 51 is inits respective ON state, a

digit is added logically to the divider associated therewith so as toadd one count to each divider to advance the state of that divider byone digit.

In the embodiment of FIG. 6, the potentials of the respective segmentedelectrodes are selectively alternated between values substantially equalto V or V,; by corresponding double throw switching elements incorrespondence with the time to be indicated, while common electrodes 46and 47 of the passive display elements are maintained at a potential VAccordingly, the potential difference between each segment of therespective segmented electrodes 41, 42, 43, 44 and 45 When a nematicphase liquid crystal is driven, it is necessary that, taking thethreshold voltage as V and the voltage sufficient for indication as Vthat said potential should conform to the following relations:

it is possible in the arrangement in accordance with the invention tosupply a voltage higher than the voltage applied to the driving circuitto the indication element as mentioned above, so that substantialadvantages such as clear visibility of indication, simplification ofdesign of driving circuit and reduction of electric power consumptioncan be achieved.

Referring now to FIG. 7, one example of a voltage boosting circuit forobtaining potentials V V, and V, from a single battery is depicted. Insuch circuit. a toroidal core 60 which provides maximum boostingefficiency while minimizing size is wound with a driving coil 63 and adetecting coil 64. Driving coil 63 is connected across the seriesconnection of a battery 61 and the emitter-collector path of atransistor 62. Driving coil 64 is connected between a resistor 65 andthe base of said transistor. An oscillating AC voltage is delivered tothe secondary coil 66 and is rectified by diodes 67 and smoothingcondensers 68 to produce the desired potentials V V,; and V whichsatisfy the conditions required in accordance with the invention.

FIGS. 8 12 are directed to an embodiment of a watch wherein a liquidcrystal display device is dynamically driven. Such dynamic driving isparticularly appropriate for use with twist-type liquid crystal displaysutilizing liquid crystals having positive dielectric anisotropy operatedin the field effect mode. Such liquid crystals and their opticalactivity are described in Schadt and Helfrich, Voltage-dependent OpticalActivity Of A Twisted Nematic Liquid Crystal, 18 Applied Physics Letters127-28 (Feb. 15, l97l). The twisted orientation of the liquid crystalmaterial is created by rubbing the inner surface of one of the plates ofliquid crystal display in a first direction and rubbing the innersurface of the other plate of the liquid crystal display in a directionoriented to said first direction. Crossed polarizers are provided, oneon each side of the liquid crystal display and oriented. in oneapplication. so that each polarizer is oriented in the same direction asthe direction of rubbing of the adjacent plate. When a voltage isapplied between electrodes deposited on the plate above a thresholdvoltage. light which normally is transmitted through the liquid crystaldisplay is cut off.

FIG. 8 represents a plot of the strength of transmitted light throughthe liquid crystal device in arbitrary units v s peak value of theapplied voltage. The applied voltage is in the form of rectangular ACpulses. The reduction in the strength of the transmitted light with theincrease in voltage. i.e.. the changing of the state of the display fromone of light to darkness or light transmission to light blocking, isdepicted. The liquid crystal cell is characterized by a clearingthreshold of voltage between one and three volts. the phenomenon beingsaturated at several volts.

FIGS. 8 and 9 show a similar plot of strength of trans mitted light vspeak value of the applied voltage where the duty ratio of the appliedvoltage is A and A respectively. A comparison of FIGS. 8 and 9 revealsthat. in the case of a duty ratio of the threshold voltage andsaturation voltage are substantially unchanged as compared with the casewhere the duty ratio is 1 (FIG. 8). However, in the case ofa duty ratioof A. the threshold and saturation voltages are shifted horizontally inthe high voltage direction. Specifically. the smaller the duty ratiobecomes the higher the saturation voltage.

Referring to FIG. Ila. a typical seven-bar display orientation isdepicted with each ofthe bars assigned a letter. In FIG. 1111. a fourdigit display, such as might be included in an electronic timepiece. isdepicted. Each of the digits are represented by a seven-bar display. thefour digits respectively displaying the numbers 0. l. 2 and 3. FIG. Ilcdepicts a series of driving waveforms for the four digit display of FIG.11b wherein said display is dynamically driven. A circuit fordynamically driving the display of FIG. 11b is depicted in FIG. 12. Theelectronic timepiece depicted includes an o scillator 70 for producing ahigh frequency time stahdard signal which is applied to divider circuit72 which produces an intermediate frequency signal from the highfrequency time standard signal of oscillator 70. The intermediatefrequency signal 72 is applied to further divider and decoder circuits74 which produce the time keeping signals in accordance with theinvention. The four-digit liquid crystal display 78 is provided withelectrodes defining seven-bar displays for each digit on one plate ofthe liquid crystal cell. All of the a bar (FIG. Ila) electrodes areelectrically connected together as are all of the b. c. .g barsrespectively so that there are seven output terminals on the plate ofthe liquid crystal cell bearing the seven-bar segments. Separate commonelectrodes are provided for each digit on the other plate of the liquidcrystal cell so that there are four output terminals on the other plate.one associated with each digit. The output of divider and decodercircuit 74 is applied to seven driver circuits 76a. 76b. 76g. each ofwhich is connected to the correspondingly lettered bar of the seven-bardisplays. Each of the driver circuits includes double throw-typeswitching elements such as are depicted in driving circuit 37 of FIG. 6,the input voltages applied to each driver being :2V and ground. Theintermediate frequency signal from divider circuit 72 is also applied toa digit timing pulse generator 80 which applies timing pulses to thecommon electrodes of the four digitss of the liquid crystal display 78.These pulses are of t voltage :V as will be seen in connection with thewaveforms of FIG. 1 It.

In FIG. 110. the output of the drivers 76a, 76b and 76f are depicted atwaveforms a. b and f respectively. These are the waveforms required todisplay the numbers shown in FIG. 11b. The timing pulses applied to therespective common electrodes are depicted in waveforms c c and q. Thenet voltage applied to the a bar of the first digit during each cycle isdepicted in the waveform a-c, of FIG. 11c.

Applying waveform a-c, to FIGS. 8 and 9, we find that upon theapplication of the first pulse, which is of a magnitude of 3V and a dutyratio of A. the display panel is saturated and becomes dark as shown inFIG. 9.

The next pulse has a peak value of -V and a duty ratio of A while thenext pulse has a peak value of V and a duty ratio of /2. Both of thesevoltages are less than the threshold voltage as shown by FIGS. 8 and 9so that the display panel becomes light although the circuit is in theOFF state. If absolute value alone is considered. the latter pulse maybe regarded as a pulse having a peak value of V and a duty ratio of A.and accordingly. is clearly less than the threshold voltage. Thealternating pulse is repeated each half period whereby each of thedigits are actuated during each period using a time-division dynamicdriving method.

It is apparent from the foregoing that it is preferable in the drivingmethod in accordance with the invention to'apply to one of theelectrodes. either the common or the segmented electrodes. a voltageless than the threshold voltage V and a voltage to the other of theelectrodes such that the net voltage across the liquid crystal cell whenit is to be rendered visible is larger than the threshold voltage. Thus.in the case of four digits to be dynamically driven. where the voltageis less than the threshold voltage is V. a net voltage of 3V may beprovided between the electrodes by proper application of the voltage tothe other electrodes. Simiarly. where 6 or 8 digits are to bedynamically driven. so that the duty ratio is /6 or /s, the voltageapplied to one of the sets of electrodes would be V. and the net voltageapplied between the electrode would be 4V and 5V respectively. Thus, asshown in FIG. 13, where six digits are provided in liquid crystaldisplay 78', the digit timing pulse generator is adapted to produce sixtiming pulses and each driver 76 is ener-. gized by 3V. As shown in FIG.14, when eight digits are provided in liquid crystal display 78', thedigit time impulse generator is provided with eight outputs and eachdriver7 is energized with i 4V.

The foregoing dynamic driving approach improves the reliability of thecircuit and reduces the number of elements by reducing the number ofleads. This results in a substantially reduced manufacturing cost.

It should be noted that with the decrease in the duty ratio. the peakvalue required for producing the same brightness increases. This resultsfrom the fact that the pulse width applied to each segment per digitdecreases as the number of digits for display increases. Accordingly.the peak value of the applied pulse voltage must be increased as theduty ratio decreases. A display cell having the same brightness can beobtained by roughly estimating the effective value which is the meanssquare of the applied electric power and applying the voltage of thatvalue.

It will thus be seen that the objects set forth above, and those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the spirit and scope of the invention. it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

lt is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed. and all statements of the scope of the invention which. as amatter of language. might be said to fall therebetween.

What is claimed is:

1. An electronic timepiece comprising oscillator means for producing ahigh frequency time standard signal; divider circuit means for producingan intermediate frequency signal and low frequency timing signals inresponse to said high frequency time standard signal; decoder means forproducing display actuation signals in response to said timing signals;driving circuit means coupled to said decoder. means and includingdouble throw-type switching means connected for selective disposition inone of first and second switching modes in response to display actuationsignals; liquid crystal display means defining passive indication meansand including at least four digits for the visual indication of time.each of said digits of said display including sevenv segmentedelectrodes oriented in a seven-bar display and a common electrode.corresponding segments of said segmented electrodes being electricallyconnected together, one of said driving circuit means being connected toeach of said commonly connected segments; and digit timing pulsegenerator means respectively connected to each of said common electrodesfor sequentially applying said first potential to each of said commonelectrodes, said double throw type switching means having first andsecond input terminals and an output terminal for selective placement ineither of said first switching mode at which said first input and saidoutput terminals are coupled and said second switching mode at whichsaid second input and said output terminals are coupled, each saidswitching means output terminal being connected to one group ofcorresponding segmented electrodes; and means for applying a second andthird potentials to said first and second switching means inputterminals, respectively. said potentials being selected to have a valuesuch that the difference between said first and second potentials issufficient to actuate said passive indication means to provide a visualindication, and the difference between said first and third potentialsis less than the threshold voltage of said passive indication means atwhich such visual indication is first produced.

2. A driving arrangement as recited in claim 1, wherein said doublethrow-type switching means includes a pair of coordinately actuatedsingle throw-type switching means, one of said single throw-typeswitching means being connected between each of said inputs and saidoutput.

3. A driving arrangement as recited in claim 1, wherein said doublethrow-type switching means comprises an N-channel and a P-channel fieldeffect transistor connected with their respective source-drain paths inseries, the respective gates being connected together for coordinateactuation. said output being at the intersection of the respectivesource-drain paths, said inputs being on the side of said source-drainpaths, said inputs being on the side of said source-drain paths oppositefrom said output.

4. 'An electronic timepiece as recited in claim 1, wherein said liquidcrystal material is characterized by positive dielectric anisotropy.

5. An electronic timepiece comprising oscillator means for producing ahigh frequency time standard signal; divider circuit means for producinglow frequency timing signals in response to said high frequency timestandard signal; decoder means for producing display actuation signalsin response to said timing signals; driving circuit means coupled tosaid decoder means and including double throw-type switching meanshaving first and second input terminals and an output terminal forselective placement in either of a first switching mode at which saidfirst input and said output terminals are coupled and a second switchingmode at which said second input and said output terminals are coupled,said double throw-type switching means being selectively disposed in oneof said first and second switching modes in response to said displayactuation signals; liquid crystal display means having at least fourdigits of display, each of said digits including seven segmentedelectrodes oriented in a seven-bar display and a common electrode.corresponding segmented electrodes of each digit being electricallyconnected together and being connected to one of said driving circuitmeans for receiving the voltage from the output terminal of the doublethrow-type switching means thereof; and digit timing pulse generatormeans connected to each of said common electrodes of said liquid crystaldisplay means for sequentially applying a first potential thereto duringassigned portions of the cycle of operation thereof; and means forapplying a second and third potential to said first and second switchingmeans input terminals respectively. said potential being selected tohave a value such that the net difference between said first and secondpotentials is sufficient to actuate said liquid crystal display means toprovide a visual indication at the segmented electrodes associated withthe liquid crystal material across which said net potential differenceappears, and the net difference between said first and third potentialsis less than the threshold voltage of said liquid crystal material atthe duty cycle of said digit timing pulse generator means at which suchvisual indication is produced.

6. An electronic timepiece as recited in claim 5, wherein said liquidcrystal material is of positive dielectric anisotropy and said liquidcrystal display is of the twist-type.

7. An electronic timepiece as recited in claim 5, including four digitsof display, said digit timing pulse generator means having a duty cycleof A, said second potential being of a voltage V less than the thresholdvoltage of said liquid crystal material at said A duty cycle, the netpotential difference between said first and second potentials beingabout 3V.

8. An electronic timepiece as recited in claim 5. wherein said liquidcrystal display means includes six digits, said digit timing pulsegenerator having a duty cycle of 1/6, said first potential having avalue of V less than the threshold voltage of said liquid crystalmaterial at said duty cycle, said net potential difference between saidfirst and second voltages being equal to about 4V.

3,881.31 1 l l 12 9. An electronic timepiece as recited in claim 5.terial at said duty cycle.the net potential difference bef Frysmldisplay mems includes F tween said first and second potentials beingequal to digits said digit timing pulse generator means having a I dutycycle of As, said first potential having a value V about less than thethreshold voltage of said liquid crystal ma- 5

1. An electronic timepiece comprising oscillator means for producing ahigh frequency time standard signal; divider circuit means for producingan intermediate frequency signal and low frequency timing signals inresponse to said high frequency time standard signal; decoder means forproducing display actuation signals in response to said timing signals;driving circuit means coupled to said decoder means and including doublethrow-type switching means connected for selective disposition in one offirst and second switching modes in response to display actuationsignals; liquid crystal display means defining passive indication meansand including at least four digits for the visual indication of time,each of said digits of said display including seven segmented electrodesoriented in a seven-bar display and a common electrode, correspondingsegments of said segmented electrodes being electrically connectedtogether, one of said driving circuit means being connected to each ofsaid commonly connected segments; and digit timing pulse generator meansrespectively connected to each of said common electrodes forsequentially applying said first potential to each of said commonelectrodes, said double throw type switching means having first andsecond input terminals and an output terminal for selective placement ineither of said first switching mode at which said first input and saidoutput terminals are coupled and said second switching mode at whichsaid second input and said output terminals are coupled, each saidswitching means output termInal being connected to one group ofcorresponding segmented electrodes; and means for applying a second andthird potentials to said first and second switching means inputterminals, respectively, said potentials being selected to have a valuesuch that the difference between said first and second potentials issufficient to actuate said passive indication means to provide a visualindication, and the difference between said first and third potentialsis less than the threshold voltage of said passive indication means atwhich such visual indication is first produced.
 2. A driving arrangementas recited in claim 1, wherein said double throw-type switching meansincludes a pair of coordinately actuated single throw-type switchingmeans, one of said single throw-type switching means being connectedbetween each of said inputs and said output.
 3. A driving arrangement asrecited in claim 1, wherein said double throw-type switching meanscomprises an N-channel and a P-channel field effect transistor connectedwith their respective source-drain paths in series, the respective gatesbeing connected together for coordinate actuation, said output being atthe intersection of the respective source-drain paths, said inputs beingon the side of said source-drain paths, said inputs being on the side ofsaid source-drain paths opposite from said output.
 4. An electronictimepiece as recited in claim 1, wherein said liquid crystal material ischaracterized by positive dielectric anisotropy.
 5. An electronictimepiece comprising oscillator means for producing a high frequencytime standard signal; divider circuit means for producing low frequencytiming signals in response to said high frequency time standard signal;decoder means for producing display actuation signals in response tosaid timing signals; driving circuit means coupled to said decoder meansand including double throw-type switching means having first and secondinput terminals and an output terminal for selective placement in eitherof a first switching mode at which said first input and said outputterminals are coupled and a second switching mode at which said secondinput and said output terminals are coupled, said double throw-typeswitching means being selectively disposed in one of said first andsecond switching modes in response to said display actuation signals;liquid crystal display means having at least four digits of display,each of said digits including seven segmented electrodes oriented in aseven-bar display and a common electrode, corresponding segmentedelectrodes of each digit being electrically connected together and beingconnected to one of said driving circuit means for receiving the voltagefrom the output terminal of the double throw-type switching meansthereof; and digit timing pulse generator means connected to each ofsaid common electrodes of said liquid crystal display means forsequentially applying a first potential thereto during assigned portionsof the cycle of operation thereof; and means for applying a second andthird potential to said first and second switching means input terminalsrespectively, said potential being selected to have a value such thatthe net difference between said first and second potentials issufficient to actuate said liquid crystal display means to provide avisual indication at the segmented electrodes associated with the liquidcrystal material across which said net potential difference appears, andthe net difference between said first and third potentials is less thanthe threshold voltage of said liquid crystal material at the duty cycleof said digit timing pulse generator means at which such visualindication is produced.
 6. An electronic timepiece as recited in claim5, wherein said liquid crystal material is of positive dielectricanisotropy and said liquid crystal display is of the twist-type.
 7. Anelectronic timepiece as recited in claim 5, including four digits ofdisplay, said digit timing pulse generator meanS having a duty cycle of1/4 , said second potential being of a voltage V less than the thresholdvoltage of said liquid crystal material at said 1/4 duty cycle, the netpotential difference between said first and second potentials beingabout 3V.
 8. An electronic timepiece as recited in claim 5, wherein saidliquid crystal display means includes six digits, said digit timingpulse generator having a duty cycle of 1/6, said first potential havinga value of V less than the threshold voltage of said liquid crystalmaterial at said duty cycle, said net potential difference between saidfirst and second voltages being equal to about 4V.
 9. An electronictimepiece as recited in claim 5, wherein said liquid crystal displaymeans includes eight digits, said digit timing pulse generator meanshaving a duty cycle of 1/8 , said first potential having a value V lessthan the threshold voltage of said liquid crystal material at said dutycycle, the net potential difference between said first and secondpotentials being equal to about 5V.